[PATCH 0/1] MR8204: comctl32: Fix use-after-free when page creation fails.

[Yuxuan Shui (＠yshui)]

When page creation fails in PROPSHEET_SetCurSel, the dialog window is destroyed, which means the
attached PropSheetInfo (psInfo) is freed. Because there is a call to PROPSHEET_SetCurSel in the
handling of WM_INITDIAG, any use of psInfo thereafter could be invalid, which wasn't taken into
account.

* * *

this feels a bit iffy but i think this is the right fix? previously we got 0 return value from `PropertySheet` because `do_loop` calls `IsWindow(hwnd)`, and when page creation failed the `hwnd` is destroyed, which resulted in `do_loop` returning 0. i just duplicated this check in `PROPSHEET_PropertySheet` too. as for the change in `DiaglogProc`, if `PROPSHEET_SetCurSel` destroyed the window then the SendMessageW isn't necessary, i believe?

also, this bit is redundant i think?

```c
      /* wizards set their focus during init */
      if (psInfo->ppshheader.dwFlags & INTRNL_ANY_WIZARD)
          return FALSE;

return FALSE;
```